selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/fs/coda/sysctl.c b/fs/coda/sysctl.c
new file mode 100644
index 000000000..0df46f09b
--- /dev/null
+++ b/fs/coda/sysctl.c
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Sysctl operations for Coda filesystem
+ * Original version: (C) 1996 P. Braam and M. Callahan
+ * Rewritten for Linux 2.1. (C) 1997 Carnegie Mellon University
+ * 
+ * Carnegie Mellon encourages users to contribute improvements to
+ * the Coda project. Contact Peter Braam (coda@cs.cmu.edu).
+ */
+
+#include <linux/sysctl.h>
+
+#include "coda_int.h"
+
+static struct ctl_table_header *fs_table_header;
+
+static const struct ctl_table coda_table[] = {
+	{
+		.procname	= "timeout",
+		.data		= &coda_timeout,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec
+	},
+	{
+		.procname	= "hard",
+		.data		= &coda_hard,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec
+	},
+	{
+		.procname	= "fake_statfs",
+		.data		= &coda_fake_statfs,
+		.maxlen		= sizeof(int),
+		.mode		= 0600,
+		.proc_handler	= proc_dointvec
+	},
+};
+
+void coda_sysctl_init(void)
+{
+	if ( !fs_table_header )
+		fs_table_header = register_sysctl("coda", coda_table);
+}
+
+void coda_sysctl_clean(void)
+{
+	if ( fs_table_header ) {
+		unregister_sysctl_table(fs_table_header);
+		fs_table_header = NULL;
+	}
+}